A runny nose indicates an irritant in the nasal passages. Because irritants also produce sneezing, these two signs tend to occur together.
Excited and nervous dogs often secrete a clear, watery mucus that drips from the nose. This type of discharge is not accompanied by sneezing and disappears when the dog relaxes.
Any nasal discharge that persists for several hours is significant. A clear, watery discharge is typical of allergic and viral rhinitis, while a thick discharge suggests a bacterial or fungal infection. A nasal discharge accompanied by gagging and retching indicates a postnasal drip. A discharge from one nostril only is seen with oral nasal fistulas and foreign bodies and tumors in the nose.
Foreign bodies, tumors, and chronic bacterial and fungal infections can erode the mucous membranes and produce a blood-streaked mucus discharge or a nosebleed. Nosebleeds also occur with bleeding disorders such as von Willebrand’s disease and hemophilia. Trauma, such as banging the nose, may also lead to some bloody discharge. If you see blood in the nasal discharge, notify your veterinarian.
Human cold viruses don’t affect dogs. However, dogs are afflicted by a number of serious respiratory diseases that initially produce symptoms similar to those of the human cold. A runny nose, along with an eye discharge and coughing and sneezing, is an indication that you should seek veterinary attention for your dog. A yellowish discharge along with coughing and fever could indicate canine influenza and you should contact your veterinarian immediately.